Cochlea implants use digital signal processing techniques to decompose an input signal into multiple frequency-filtered bands, which are then transmitted to an electrode array implanted in the scala typmani for direct stimulation thereof. While cochlea implants do deliver significant auditory functionality to patients with profound hearing loss, there are still problems with the cochlea implants.
For a healthy ear with functioning cochlea, there is a tonotopic mapping from frequencies in the sound signal that excites the round window to the place of excitation on the cochlea, and further to the auditory nerves that converts the motion of the basilar membrane at that point to nerve signals.
The cochlea performs the function of frequency dispersion by causing sound input at certain frequencies to vibrate at some locations and other frequencies to vibrate at other locations on the basilar membrane. It has been shown that high frequencies lead to maximum vibrations at the basal end of the cochlea coil and low frequencies lead to maximum vibration at the apical end and stimulation of the nearby auditory cells. The tonotopic organisation of the basilar membrane is therefore followed by a tonotopic organisation of the auditory nerves, which means that a given auditory nerve is associated with the frequency corresponding to its position on the basilar membrane.
When implanting the electrode array in the scala typmani the frequency mapping that associates each electrode with the frequency corresponding to the nearest auditory nerve is not known due to variations in length of basilar membrane, insertion depth, etc.
Cochlea implant bypasses the middle ear, basilar membrane and stimulates the auditory nerves directly. This means that electric signals may be transferred directly or indirectly to cochlear nerve and/or to auditory cortex of the user. Hence, the aforementioned tonotopic mapping provided by the basilar membrane is not available for cochlea implants, as the sound is not converted to nerve signals by the ear.
A Cochlear Implant typically includes i) an external part for picking up and processing sound from the environment, and for determining sequences of pulses for stimulation of the electrodes in dependence on the current input sound, ii) a (typically wireless, e.g. inductive) communication link for simultaneously transmitting information about the stimulation sequences and for transferring energy to iii) an implanted part allowing the stimulation to be generated and applied to a number of electrodes, which are implantable in different locations of the cochlea allowing a stimulation of different frequencies of the audible range. Such systems are e.g. described in U.S. Pat. No. 4,207,441 and in U.S. Pat. No. 4,532,930.
In an aspect, the hearing device comprises multi-electrode array e.g. in the form of a carrier comprising a multitude of electrodes adapted for being located in the cochlea in proximity of an auditory nerve of the user. The carrier is preferably made of a flexible material to allow proper positioning of the electrodes in the cochlea such that the electrodes may be inserted in cochlea of a recipient. Preferably, the individual electrodes are spatially distributed along the length of the carrier to provide a corresponding spatial distribution along the cochlear nerve in cochlea when the carrier is inserted in cochlea.
For end-users with unilateral deafness, pitch mapping and other objective measures such as ASSR, can be used to obtain the mapping from acoustic frequency to electrode position. However, that is not possible for bilateral deafness as there is no healthy reference to which the mapping can be compared to.
Hence, an improved cochlea hearing system, in particular suitable for bilateral deaf people, further an improved method of operating a cochlea hearing system, would be advantageous. Bilateral deaf people may e.g. have two implants, one at each cochlea.
It is a further object of the present disclosure to provide an alternative to the prior art.
In particular, it may be seen as an object of the present disclosure to provide a cochlea hearing system and/or method for operating a cochlea hearing system, that solves, at least alleviates or provides an alternative the above mentioned problems of the prior art.